1. Field of the Invention
This invention relates to a hydroxylapatite base porous filler for an organism and a method of producing the same, which porous filler is suitable to be filled to an injured or diseased part (having a large bone loss) of the bone tissue for the purpose of achieving an early cure to promote rebirth of bone.
2. Description of the Prior Art
Hitherto, in case a bone of a human or an animal is partially cut out for the reason of an injury due to a traffic accident or the like and of a tumor or infection disease, an apatite block having a biocompatibility with a natural bone has been extensively used for curing a lost part. In this case, the apatite block inserted in a body for curing is usually joined with the natural bone. In the treatment of the bones and joints infections, especially clonic osteomyelitis, dosage of a pharmaceutical has been carried out under oral administration and/or injection in order to prevent a suppuration of a part of body subjected to the surgery and to promote the cure of the same.
However, difficulties have been encountered in the above-discussed curing method for the bone. That is to say, dosage of the pharmaceutical raises the concentration of the pharmaceutical uniformly throughout the whole organism body, so that a healthy part other than the injured or diseased part is also exposed to the pharmaceuticals thereby causing a possibility of making a side effect. Thus, it is difficult to raise a local concentration of the pharmaceuticals only at the injured or diseased part. Additionally, the pharmaceutical uniformly distributed throughout the whole organism body is decomposed and excreted under the action of various internal organs, and therefore the pharmaceutical concentration at the injured or diseased part is rapidly lowered.
In this regard, it has been proposed to use a means for gradually releasing the pharmaceutical. An example of such a proposition is disclosed in Japanese transactions of "Central Japan Orthopedics Disaster Science Society" Vol. 31, No. 5, annex, Pages 1882 to 1885, issued in 1988. In this proposition, bone cement beads formed of polymethylmethacrylate containing 3-4-dideoxykanamycin B is filled in the bone marrow at an injured or diseased part.
Further, mixing a variety of antibiotic materials with the synthetic resin-made cement beads is disclosed in Japanese transactions of "Central Japan Orthopedics Disaster Science Society" Vol. 32, No. 3, annex, Pages 1035 to 1040, issued in 1989.
Furthermore, Japanese transactions "Joint Surgery" Vol. 8, No. 12, Pages 65 to 71, issued in 1989 discloses the following: Synthesized hydroxylapatite fired at 900.degree. C. is transplanted to a bone lost part in view of the fact that the main component of an animal's bone is hydroxylapatite. This transactions also shows that the transplanted synthesized hydroxylapatite is high in biocompatibility with a natural bone in an animal's body and exhibits an excellent curing effect.
Moreover, a Japanese technical magazine "Biomaterials" Vol. 8, No. 1, Pages 11 to 22 discloses the fact that hydroxylapatite which has been prepared by a wet synthesis was transplanted to a matured rabbit. The magazine also shows that transplanted hydroxylapatite exhibited an excellent biocompatibility with an organism bone, that formation of a new bone in direct contact with the synthesized hydroxylapatite was recognized, and that the compression strength of the bone at the implanted part increased until a time of several weeks after the implantation.
Of the above-discussed conventional techniques, one using the apatite block has a problem that growth of a new bone is slow at a joint part of the apatite block and the natural bone in the organism body after a surgery and treatment. One in which the apatite block and the natural bone are joined with each other by means of the metal piece has a problem of requiring removing the metal piece by carrying out a further surgery.
Additionally, the conventional synthesized hydroxylapatite can be formed porous as same as an organism bone in accordance with firing conditions. However, the conventional synthesized hydroxylapatite has a considerably fine and minute structure from a view point of absorbing and expelling the pharmaceutical, and therefore it is considerably low in porosity and has a low absorption amount of the pharmaceutical.
One in which the pharmaceutical is contained in the synthetic resin-made cement beads is disadvantageous because the cement beads remain in the organism body even after a predetermined amount of the pharmaceutical has been gradually released, thereby affecting the focus. Additionally, the synthetic resin-made cement beads are insufficient in amount of the pharmaceutical kept therein and in a time period throughout which the pharmaceutical is gradually released.